1. Field of the Invention
The present invention relates to an apparatus for and a method of displaying a pseudo-three-dimensional image, as viewed from a certain viewpoint, of a moving object whose three-dimensional coordinates and rotational angles have been established, such as a game character in a displayed video game image, and a machine-readable recording medium which stores a computer program for displaying such a pseudo-three-dimensional image.
2. Description of the Prior Art
There have heretofore been known pseudo-three-dimensional image displaying apparatus for displaying and controlling a moving object such as a game character in a displayed video image depending on control actions made by a game player, and game apparatus including such pseudo-three-dimensional image displaying apparatus. Recent years have seen game apparatus which incorporate the advanced computer graphics technology for storing all data of moving objects, scenes, and obstacles as polygon data, and displaying images including such moving objects, scenes, and obstacles as viewed from a certain viewpoint in a certain direction. Polygon data normally have at least three-dimensional coordinates corresponding to the vertexes of polygons, and moving objects, etc. are actually three-dimensional objects. Since, however, display units such as CRTs or the like for displaying video images have a two-dimensional display screen, the display units display images of such moving objects, etc. as viewed from a certain viewpoint as images that are projected onto such a two-dimensional display screen, i.e., pseudo-three-dimensional images which look pseudo-three-dimensionally on the two-dimensional display screen.
Viewpoints from which game images are viewed vary depending on the contents of video games played on video game apparatus. For example, in a video game in which the game player moves a displayed character along a certain path, such as a driving video game, the viewpoint is fixedly established along the direction in which the character moves and behind the character. In video games in which the game player can move a character relatively freely in a given field, such as martial-arts games, sports games, etc., the viewpoint is fixed at a distance position from which the character as it moves can be observed or at a position from which the character as it moves can be followed, as if viewed from a television camera viewpoint.
In the conventional pseudo-three-dimensional image displaying apparatus, the viewpoint from and the direction in which a moving object such as a character is viewed are established depending on the present position and direction of the moving object. This image viewing principle poses no problem with respect to video games, such as sports games, which will not make the game player feel odd even when the viewpoint of the game player is not the same as the viewpoint in the displayed images. However, in video games, such as driving video games or the like, in which the viewpoint of the game player should preferably be the same as the viewpoint in the displayed images, the game player may feel odd because the viewpoint of the game player may not be the same as the viewpoint in the displayed images according to the above image viewing principle.
Reasons why such a problem occurs will be described below with respect to a driving video game. In the driving video game, a viewpoint may be established in some instances to reproduce a scene as viewed from the driver in a car on the display screen. In such a case, the viewpoint is usually established in order to view a front scene from a certain position in the car through the front windshield of the car. Insofar as the car is running at a constant speed in a fixed direction, the field of view of the driver is substantially the same as the field of the image that is being displayed on the display screen. However, when the car driven by the driver makes a turn, the driver is swung laterally under centrifugal forces, and its position relative to the car changes, resulting in a possible discrepancy between the field of view of the driver and the field of the image that is being displayed on the display screen.
One solution would be to simulate forces acting on characters, i.e., the car and the driver, and calculate a viewpoint from and a direction in which a front scene is to be viewed depending on the calculated forces. However, if a strict simulation process is to be carried out to establish an accurate viewpoint, then the number of parameters to be taken into account will be greatly increased and the time required to calculate the forces will also be greatly increased, making it difficult to effect real-time simulation processing. In the driving game, since the car (character) basically moves in a two-dimensional plane, behaviors of the character can physically (dynamically) be simulated relatively easily. However, character behaviors cannot accurately be simulated for video games which employ characters such as airplanes that move freely three-dimensionally in midair.